Facile 2D In2Se3 protection for enhanced BiVO4 stability in highly alkaline photoelectrochemical water splitting

Abstract

Photoelectrochemical (PEC) water splitting holds promise as a major source of sustainable energy production in the future. However, stable photoelectrodes for long-term use, particularly in harsh environments, remain challenging for large-scale PEC applications. Herein, this study reports facile, rapid, and scalable deposition of two-dimensional (2D) In₂Se₃ protection layers to improve the photoelectrochemical performance and stability at pH 12.3 and pH 13, where bismuth vanadate (BiVO₄) is typically unstable. BiVO₄/In₂Se₃ achieves a photocurrent density of 12.38 mA cm⁻² at 1.23 V vs. reverse hydrogen electrode (RHE) under 455 nm (39 mW cm⁻²) LED light illumination at pH 12.3. The suitable energy alignment of In₂Se₃ boosts hole extraction from BiVO₄ and prolongs the lifetime of holes before recombination. The photoelectrochemical stability tests reveal that the In₂Se₃-protected BiVO₄ achieved over 40 h stability at pH 12.3. Studies on the corrosion mechanism of BiVO₄/In₂Se₃ show that the oxidation of In₂Se₃ by the hole accumulation at the surface destabilizes its lattice structure, which impedes the formation of chemically stable In₂Se₃ in the given chemical environment. Therefore, a catalyst layer or a fast-kinetics reaction medium is required to utilize the accumulated holes at the surface, which enables the long-term use of protective layers in alkaline environments.